Region, as the compulsory keyword, is followed by its identification number. The list of signed identification numbers of surfaces, patches, and shells bounding the region is specified after appropriate model entity keyword ( surface, patch, or shell) preceded by keyword boundary. The positive number means that the outer normal of the surface, patch, or shell points out of the region, the negative number indicates that the outer normal points inside the region. The list of identification numbers of regions surrounded by the region may be specified after keyword subregion. If a subregion is touching the region along its boundary surface, patch, or shell, this boundary entity must be specified also in the appropriate list of entities bounding the region (including proper orientation). Furthermore, the identification numbers of vertices, curves, surfaces, patches, and shells inside the region can be enumerated after appropriate model entity keyword ( vertex, curve, surface, patch, or shell) preceded by keyword fixed. The meaning of keywords size, factor, and property is the same as in Section Input Record of a Patch. Keyword hole indicates that currently defined region is a hole. The output of tetrahedrons in region may be enforced or suppressed by setting yes or no after output keyword. By default, each physical solid region is designated for output.